The present disclosure relates generally to passive downhole chemical release packages and more particularly, in certain embodiments, the present disclosure relates to passive downhole chemical release packages capable of releasing chemical agents at desired locations in a well bore and associated methods.
A wide variety of chemicals may be used within a well bore in connection with producing hydrocarbons or reworking a well that extends into a hydrocarbon formation. Chemicals such as free radical initiators, catalysts (e.g. cement curing agents, gelling agents, mud-to-cement agents, etc.), lubricants, contrast agents, acid gas scavenger materials (for H2S, CO2, etc.), filter-cake breakers, sensors, and indicators are commonly used. Such chemicals are well known in the art.
A persisting problem in the drilling of wells is the ability to trigger chemical reactions downhole on demand. Two different flow regimes may be required to properly stage downhole reactions in a conventional operation: Laminar flow, taking place at a relatively slower rate, is needed to place the chemical of interest at a desired depth, while turbulent flow, requiring a fast pumping rate, would be needed to mix chemicals. The transient pressure changes induced by changing the pump rate of the fluids may be enough to cause undesired well bore instability. These considerations are exacerbated by the long length scale of the drillstring and the continuous flow of fluids through the drill pipe and the annulus, making it difficult to stage the mixing of any two reagents at a specified depth or location, or to initiate their desired reaction at a specified time. As a result, companies and personnel managing drilling rigs are often resistant to the practice of changing pump speeds to facilitate the requirements of drilling fluids over the course of applications.
One approach proposed in the past is to use encapsulated or otherwise protected chemicals which are added to fluids at the top of the drill string and pumped down the well bore. The encapsulating material could be tuned to degrade at a predetermined condition naturally occurring along the drillstring, which typically has gradients of increasing temperature and pressure with increasing depth. The limitation of this approach is that the encapsulated chemical could only react with other chemicals nearby in the suspending fluid, within a spatial zone governed by diffusion and turbulent mixing, or on a limited length scale.
It may be desirable to have a deployment means to release one or more chemicals into the annulus between the well bore and the casing so that the chemicals need not be pumped from the surface at the top of the well bore. Such an approach could be used to protect surface equipment such as pumps, lines, tanks, mixers, or solids control equipment from reactive chemicals.